1. Field of the Invention
This invention relates, generally, to medical appliances. More particularly, it relates to an adapter having utility in connection with Luer valves.
2. Description of the Prior Art
A Luer fitting or tip is a rigid, cylindrical-in-configuration, slightly tapered member that is formed on the leading end of the barrel of a common medical syringe. More particularly, it is a truncate tube that provides fluid communication between the interior of the barrel and the external environment.
Although it is mechanically possible to connect a catheter directly to a Luer fitting, such a direct connection is seldom made because non valved catheters use a rubber plug through which a needle is pushed. Just as importantly, such a direct connection is unvalved and there is usually a need for a valving function between a syringe and a catheter.
The Luer fitting and catheter are normally interconnected by an adapter member, known as a Luer valve, also of generally tubular construction, that firmly engages the catheter at a first end and the Luer fitting at a second end, thereby providing a reliable interconnection between the Luer fitting and the catheter.
The common adapter is provided with a check valve so that the contents of the barrel pass freely through the adapter into the catheter when the plunger of the syringe is advanced and so that reverse flow from the catheter to the barrel is not possible.
The adapter now in widespread use has a rigid plastic body and an elastomeric, slidably mounted check valve member disposed therein. Insertion of the Luer fitting into the second end of the adapter displaces the elastomeric check valve in an axial direction; this unseats the valve and permits fluid flow from the syringe barrel to the catheter. Part of the check valve is distorted or compressed as a result of the axial displacement, but the resiliency of said valve restores it to its undistorted configuration and hence to its seat when the Luer fitting is removed and reverse fluid flow is blocked. However, if the amount of distortion is too great, the check valve will not resume its position of repose, and unwanted reverse flow of fluid from the catheter may occur.
The prior art contains no teachings or suggestions that would advise one of ordinary skill in this art how to design the check valve of a Luer fitting adapter so that it is not subject to failure.
Although Luer fittings are important medical parts that are purportedly manufactured according to strict specifications, it is well known in the medical field that the respective diameters of a group of Luer fittings will vary widely. When the diameter of a Luer fitting is too small, it can easily withdraw from the adapter. When it is too large, it can break the adapter.
Between these two extremes, almost no Luer fitting is ever encountered that perfectly mates with its adapter. As a result, health care professionals have become accustomed to jamming together Luer fittings and their adapters, even though it is widely known that this can result in catastrophic failure of the medical procedure about to be undertaken. For example, if the elastomeric check valve within the adapter is overly distorted, as aforesaid, and fails to resume its flow-blocking position when the Luer fitting is withdrawn, the substance passing through the valve enters the balloon of the catheter. For example, sterile water would enter the balloon of a urinal catheter, and air would enter the balloon of an endotracheal tube.
Similarly, if the health care professional jams the Luer fitting and the adapter together, the check valve may not open fully in accordance With its design.
The inventors who have studied this problem in the past have all come up with the same solution: Improvements in the manufacture of Luer fittings designed to reduce the variations in dimensions of said fittings. This approach has not worked, because Luer fittings are made in vast quantities at high speed, and it is impractical to even hold out the hope that manufacturing tolerances can be improved to the degree needed.
There is a need for a better way to interconnect Luer fittings and catheters, but the prior art, when considered as a whole in accordance with the requirements of law, neither teaches nor suggests how this seemingly intractable problem could be overcome.